Automatic conditioned air system with compensation for clogging filter



cit. 2Q, 3953 B. G. COPPING 2,656,112

AUTOMATIC CONDITIONED AIR SYSTEM WITH COMPENSATION FOR CLOGGING FILTER Filed July 7, 1949 5 Sheets-$heet 1 In Van Lar' Bruce G. Capping Oct. 26, 1953 B. G; COPPING AUTOMATIC CONDITIONED AIR SYSTEM WITH 7 COMPENSATION FOR CLOGGING FILTER a sheets-sheet 5' Filed July 7, 1949 In rent 02" brace 62' flopping Patented Oct. 20, 1953 AUTOMATIC CONDITIONED AIR SYSTEM WITH COMPENSATION FOR CLOGGING FILTER Bruce G. Capping, Atlanta, Ga., assignor to Don Manufacturing Company, Chicago, 111., a corporation of Illinois Application July 7, 1949, Serial No. 103,376

The present invention relates generally to methods and devices suitable for operating temperature conditioning systems and it may be noted that the instant invention finds a particularly useful application in a pressure operated control system adapted for the regulation of a forced circulation air conditioning system,

Many living units and business establishments today are provided with temperature conditioning systems which depend upon the forced circulation of heated or cooled masses of air to attain desirable temperature standards within a space or room. Conditioning systems of this type are often times equipped with registers adapted to control the volume flow of air into the room or space being temperature conditioned. In accordance with the teachings of the art, these registers are sometimes controlled by means of thermostats which respond to temperature variations within the space or room.

It has been found, however, that individual register control alone is inadequate because it is of vital importance that the total heat transferred in the conditioning unit or heat exchanger also be regulated so as to be nearly proportional to the total heat transmission load of the tem.- perature conditioning system;

In a warm air heating system wherein each individual room or space is provided with a thermostatically controlled register, opening and closing of the various registers will result in a pressure variation in the main air duct. This pressure variation is reflective of and proportional to the average degree of opening of all of the individual thermostatically controlled registers in the system. As the average degree of register opening increases, the pressure in the main air duct of the warm air heating system will fall and as the average degree of re ister opening decreases, the main air duct pressure will rise.

Inasmuch as the average degree of register opening is proportional to the average heat loss from the living unit Or business establishment, it follows that the pressure in the main air duct of a warm air heating system is-proportional in a determinable degree to the average heat loss from the entire living unit or the business establishment.

It is, therefore, an object of this invention to provide a pressure operated control system for a temperature conditioning system whereby the heat transmission of a temperature conditioning means may be controlled in response to variations of pressure within the main circulating duct of a temperature conditioning system. I

3 Claims. (01. 236-11) It is well known that most temperature conditioning systems of the type wherein a forced circulation of masses, of heated or cool air is utilized to temperature condition a living unit or a business establishment employ air filters in the return air system so as to provide for the removal of any foreign particles which maybe carried by the circulated air.

It is also well known that filters provided for this purpose present a certain resistance to the circulation of air which varies in proportion to the degree of contamination of the filter. Although the resistance created by a clean filter element may be almost negligible, the increased resistance resulting when a filter becomes clogged and contaminated seriously affects the pressures attainable in the rest of the temperature conditioning system.

In a temperature conditioning system provided with individually controlled thermostatic registers and a filter controlled return air system, it follows that th main air duct pressure variation will not be a true and consistent index of the average heat loss of a living unit or a business establishment unless the variable resistance of the filter element is compensated for in some manner.

It is, therefore, another object of my invention to provide a pressure operated control system for a temperature conditioning system wherein complete compensation for variable filter pressure is provided so that the control system will function accurately regardless of the degree of filter contamination.

It is also desirable in the regulation of temperature conditioning systems to make provision whereby response may be had to the temperature gradients existing between the various temperatures in the room or space to be temperature conditioned, the ducts of the heating system per se, and the atmospheric temperature.

A control system thus provided is adequately equipped to anticipate and respond to sharp changes in temperature resulting from rapidly changing atmospheric conditions.

Therefore, it is another object of this invention to provide a pressure operated control system for a temperature conditioning installation which may be used in combination with compensating devices, for example, an indoor-outdoor thermostatic control.

According to the general features of the present invention a pressure sensitive control device is provided with a flexible bellows operative to actuate switch means in response to pressure variations within a temperature conditioning system. One form of such a control device disclosed herein provides a plurality of flexible bellows which are arranged so as to permit a compensating reaction of one selected pressure gradient within a temperature conditioning system by one or more additional selected pressure gradients. The switch means is placed in control of an electric circuit connected to a temperature conditioner such as afurnace. This invention further contemplates the provi sion of compensating devices in series with the pressure sensitive control device,-for example, an indoor-outdoor thermostatic control.

It is believed that my novel methods of controlling a temperature conditioning system will best be understood from the description of the structure provided for practicing the same. The novel features which I believe to be characterlstic; ormyinvention as well as the general organization and method of operation will become apparentto those versedlin the art through reference to the following detailed' description and the accompanying drawings in which;

Figure l is a diagrammatic view of a forced warrn air heating system adapted for automatic control in accordance with the teachings of the present invention;

Figure 2'is' a plan View of a pressure sensitive control device embodying the principles of my ve i Figure 3 is an end elevational view of the pressure sensit'ive control device illustrated in Figure ;2;

jFigure 4 is a cross-sectional view taken on lineIVIV:of Figure 2;

Figure 5 is a plan view of a pressure sensitive control device embodying the principles of my invention but modified to omit certain structurs for accomplishing compensations thereof;

Figure 6 is an end elevational view of the pressure sensitive control device shown in Figure 5; and" Figure 7 isa diagrammatic view of a forced warm air heatin system similar to that shown in Figure 1 but augmented by an indoor-outdoor thermostatic control.

ls hown on "the drawings:

Referring to Figure 1, an elementary fbfced warm 'air'sys'tem is ai grammaucauyshcwn and campuses a furn ce. ii), an air duct H, all 'ailt'O- maiti thermdstaucauy controlled register I2; the or more l'b'dms 13, a return duct I4, an air filter I5 and a blower It. The basic system is shown as being augmented by a pressure sensitive control device indicated generally by the referen'ce numeral [1' and a furnace control defic'e'indicat'ed at l8. I

As may be seen on Figure 1, the pressure sellsiti've cblitrol devic "I1 is placed in ccmmunica= use with the system at 'a plurality or points which bear a special relation to prc-se'ledte'd pressure conditions. "These points ofcomm'uni catio'n are identified by the reference symbol Pa for pressure at the discharge of the blower l6; Pa for the pressure at the suction side of the blower 'IB and 'Pr 'for the pressure of the air entering the filter l5. For convenience in exe planation, the additional reference symbol Pr is used to indicate the air pressure in the room T3.

Turning now to Figures 2, 3 and the pressure sensitive control device it is shown as including an outer bellows plate l9 which is attached at upper edge to abrac'ket 2% by means of a flexible strip 2 l 'The bracket" 251s pioi i'ded'with an ininner bellowsplate 2?.

.4 tegral backing portion which is identified as a main back plate 253a,

Situated in spaced relationship intermediate the main back plate 25a and the outer bellows plate- It are a pair of bellows supports 22, and 23. Asmay be seen onLFigureB; the bellows supports 22 and 23 are assembled in fixed relationship with the bracket 20 by means of suitable end members 2 which may be fastened to the main back plat -Zllc'by any suitable fastening means- An-outerbellow's 25 made of a flexible material and formedin-the-usual manner is sealed to the outer bellows plate is on one side and the other side is sealed'to the bellows support 22.

Anintermediate bellows 26 is sealed to the bellows support 23 and the other side is sealed to an An inner bellows 39 is sealed; to the inner bellows plate 21 on one side and the other side is sealed to the main back plate Zlla.

'Air'communication is established withthe various bellows by means of a filter intake pressure tube ifi'whichenters the interior of the bellows 3 9; a blower suctionfp'ressure tube ii, which enters'the interior of the intermediate bellows 2 f, anda' blower discharge pressure tube 82, which enters the interior of the bellows 25. The pressure tubes ail, it and 2-2 are designated by like reference numerals-upon the diagrammatic view of a forced warm air heating system shown in Figure l.

The inner bellows plate 2? is hinged by'means of a flexible strip 29 to a bracket i secured to the main baclc plate 20a and is therefore movabl'y responsive to the pressuresin the intermediate bellows 2% andthe inner b'ellowsfifi.

In order to transmit-the resulting movement of the inner bellows plate 2?; a pair of suitably ext-ending lugs are provided as atl'ia, which extend through slots 2 3a formed in the end members 2 5, to engage lan adjustable member carried by the outer bellows plate l9.

As may be seen on the drawings the outer bellows plate 19 is providedwith a projecting guide pin 39 and 'a' threaded stud 3i which arearranged upon the outer bellows plate in spaced relation ship upon a substantially cente A slotted T-shaped member 32 promded with a lengthy slot 32c and a. pair of pressure feet 321) is arranged upon the face of the outer eel r plate is for sliding adjustment relative the Thus, the threaded 3! may receive an justing nut 33 in threaded relationship therewith whichm'ay be drawnup tightly to maintain the l' shap'ed member 32 in any desired adjusted pesition; It will be noted that the pressure feet 321) of the T-shaped member 32 are arranged for contact engagementwith the projecting lugs 21s ofjt-he inner bellows plate 27 Since the outer bellowsplate i3 hinges around the flexible strip 2!, it will be apparent that adjustable positioning of the T-shaped member .32 along the face of the outer bellows plate is will vary the point of contact engagement between the pressure feet 32b and the lugs 'E'ic thereby ermitting selective adjustment of the leverage of theinner bellcws plate '2! upon the outer bellows plate 19' as may be desired.

A hook 34 is fixed to the main bacl: plate 227:: and receives a small resilient member '35 which y e the form of a coil spring. The other end of the resilient member 35 is attached to a heel; formed on the end of a threaded stud 36 which is adapted to pass freely through "the outer bellows p'l'ate l9. The amount of tension exerted by the resilient member 35 upon the outer bellows plate may b selectively adjusted by means of a knurled adjusting screw 31 received on the threaded stud 36.

A sensitive switch 38 which is normally open may be interposed between the main back plate 20a and the outer bellows plate I9 and is arranged in such a manner as to be actuated to a closed position Whenever the outer bellows plate I9 moves inwardly beyond a certain predetermined point.

It will be evident that the blower discharge pressure Pd will be manifested as a positive force whereas the filter intak pressure Pr and the blower suction pressure PS will both be manifested as a negative force. Therefore, the blower discharge pressure will tend to force the outer bellows plate I9 outward against the pull of the resilient member 35 which may be considered a control spring. The negative blower suction pressure will tend to draw the inner bellows plate 21 to the right and thus a force will be transmitted through the pressure feet 32b thereby assisting the blower discharge pressure in forcing the outer bellows plate I9 outwardly. The filter intake pressure, also negative, will tend to draw the inner bellows plate 21 inwardly and will thus oppose and subtract from the outward force of the blower suction pressure Thus, the force tranmitted to the outer bellows plate I9 will be a certain proportion of the pressure drop through the filter I5, the proportion depending upon the setting of the T-shaped member 32.

Referring again generally to Figure 1, this operation may be explained with respect to the enviromnent of a complete heating system. It will be evident that in the system shown, there are two points of variable resistance, namely, at the filter I5 and at the thermostatic register I2. All other resistances will be fixed for any particular heating system. If it is assumed that the filter resistance does not change, it will be evident that asthe register I2 opens and closes, the blower discharge pressure Pd will fall and rise in a proportional relationship to the degree of register opening. However, if the resistance offered by the filter I5 is not constant it will have an effect upon the blower discharge pressure Pa which will combine with the pressure varying effect resulting from the changes in register opening. Thus, the pressure obtained at the blower discharge will be decreased due to the filter resistance by an amount which will be a fixed fraction of the pressure drop through the filter.

It follows that a pressure sensitive control device I'I when incorporated in a heating system similar to that shown in Figure l is arranged to respond to the various pressures as shown, the net pressure exerted on the outer bellows plate I9 will be equal to the blower discharge pressure plus a, certain fixed proportion of the amount of the pressure drop through the filter I5.

In operation, as the temperature of the room I3 rises, the thermostatic register I2 will close and thereby produce an increase of not pressure on the outer bellows plate I9. This increase in pressure will tend to force the bellows plate I9 outward and when a predetermined pressure has been reached,the switch 38 will be actuated to an off position. The switch 38 may be interposed in an electric circuit leading from a source S to the burner control device I8. When the switch 38 is actuated toits off position the burner controlled by the'b'u'rner control device I8 will be deenergized.

As the room I3 cools, the thermostatic register I2 will open thereby reducing the net pressure at the pressure sensitive control device I! and the outer bellows plate [9 will move slightly inward thereby permitting the switch 38 to be actuated to its closed position to complete the:

electric circuit and start the burner controlled by to the actual overall heat requirement of the room.

It will be understood, of course, that the method of control herein described and the pressure sensitive control device provided for practicing this method are equally adaptable to regulate the operation of a temperature conditioner as and for cooling. It may also be noted that equally efiicient control could likewise be established if the furnace it were replaced by a temperature conditioning unit adapted for combination heating and cooling.

Referring now to Figures 5 and 6, a modified form of pressure sensitive control device is indicated generally by the reference numeral 45 and is shown as comprising a bellows plate 45 which is hinged to a brackekt 4'! by means of a flexible strip 48. The bracket 41 is provided with a main back plate portion 59. A bellows 50 made of a flexible material and shaped in the usual manner is sealed on one side to the bellows plate 56 and on the other side to the main back plate 49.

A clip angle 5! is provided on one end of the bellows plate as and is provided with a projecting portion em for carrying a control spring 52 and a second projecting portion Bib which may be arranged in actuating position with a sensitive Switch 53.

The other end of the spring 52 may be attached to a threaded stud 54 which passes through the main back plate 69 and is threadedly engaged by a knurled adjusting nut 55. The amount of tension exerted by the spring 52 in biasing the bellows plate it towards the main back plate :39 may be selectively adjusted by turning the nut 55 on the threaded stud 54.

A pressure tube 56 enters the interior of the bellows 50 and may, for example, place the bellows 50 in air communication with the plenum chamber or main air duct of a temperature conditioning system. Y

It will be apparent that as variations in air pressure occur within the plenum chamber or main air duct of the temperature conditioning system the bellows 50 will expand or contract and thereby force the bellows plate 46 to pivot relative to the bracket Ell through the hinge joint of the flexible strip 33. When this occurs, the clip angle 5| will be moved against the spring bias of the control spring 52 and the projection 5Ib will be actuated relative to the sensitive switch 53.

Thus, if the sensitive switch 53 is normally closed and is placed in control of a temperature varying source such as a control burner or a cooler unit, a pressure increase in the bellows 50 in response to a lower heat transfer requirement placed upon the temperature conditioning system will cause the bellows plate 46 to move outwardly and the sensitive switch 53 will be actuated to an open position.

Conversely, if a greater heat transfer requirement is placed upon the temperature condition advantageous to use, in conjunction with the compensating pressure cont'rol:described above, a so-called indoor-outdoor thermostatic control. Referring particularly toFigure '7, an arrangement is shown whereby suchaq-thermostatic control is employed;

Asshowninliigure'l, a temperatureconditioning system. is diagrammatically illustrated as comprisinga furnace. l, and 'air duct H for delivering temperature conditioned air to an automatic thermostatically controlled. register situated inv airoom outletiln'otshown) .a return duct 14., an :air' filter l and a blower lfif.

According to this; invention, the basic system is Iaugmentedby apressureisensitivet control deviceindicated generally 'by the reference numeral l'l and aiurnace control device indicated at,

I8. Theindoon-outdoor thermostatic control is shown as comprising a thermostatic bulb 63 which is placed outsideiof the structure to be heated, :herein indicated by the reference numeral 6|, so as to be exposed to atmospheric temperatures; Asecond thermostatic bulb t2-is placed inthe bonne'tof thetfurnace It. The thermostatic bulbs 60 and 62 may "be a'ctuatingly connected-to a conventional thermostatic control device indicated generally bythereferencenumeral 63. The thermostatic control device 53, the furnace controlld'eVicefl'B and the pressure sensitive controldevice Lil" may be interposed in an electric circuit in series connection with .one another. The electric circuit containing such components is-s'ho'wnon Figure 7 as leadingfrom a source -S' through-a transformer 6 The addition of the indoor-outdoor thermostatic contro1 functions to maintain the bonnet temperature of the furnace It at a level .inversely proportional to the outside temperature as measured by the thermostatic bulb til. Thus, if the outside temperature is low, the bonnet temperature will be high. By placing sucha' controlin series with the pressure sensitive control device El", theswing of the bonnet temperature wil1 be limited and the entire temperature conditioning system will yield-a more con sistent performance.

From the foregoing it should be seen that I 8... pressure variables 7 within the temperature. conditioning system.

It will be understood that modifications and variations may be effected without departing from the scope of the novelconceptsof the present invention.

I claim as a my invention:

'1. In a temperature conditioning system for an enclosure and including a blower having an inlet and an outlet, means coupling said inlet .to the enclosure including a filter and means couplingv said outlet tothe enclosure including a temperature conditioner and damper means responsivev to temperature within the. enclosure. means controlling said temperature conditioner comprising means responsive to the gaugepressure :at the blower outlet .and causing. operation of said temperature conditioner when'said'gauge pressure drops below an adjustable value; and

means responsive to the difierential inpressure' across the filter for reducing .said adjustable value assaid difierential in pressure increases, thereby to act in a compensating direction-for variation inthe resistance of the filter.

2. In a temperature conditioning apparatus :for an enclosure including a fluidfiow system having an inlet and anoutlet to and from saidenclosure and means'ior circulating fluid in said system, a filter in said system, means for throttling the flow of fluid insaid system to change the pressure therein for controlling the-conditioning of the enclosure,=-means responsive tosaid throttled pressure to' effect operation of said conditioning meanswhen the throttled pressure is changed to one side of anadjustable value, and compensating means responsive to a false change inthrottle pressure, efiectedby the clogging of said filter, to adjust saidresponsive means and adjust compensatingly said adjustable value.

3; In a temperature conditioning apparatus for an enclosure including a fluid flow system having an inlet-communicating with said enclosureand means "for'circu'lating fluidin-saidsystem, a filter in said-system, means for throttling the flow of fluid in saidsystem to change the pressure therein for controlling the conditioning of the enclosure, means responsive to said throttled pressure-"to efiect operation of said conditioning means when the throttled pressure is changed to one side of an adjustable value, and compensating means responsive to a false change in throttle pressure, effected by the-clogging'of said filter, to'adjust said responsivemeans and adjust compensatingly said adjustable'value, said throttling means being located at said enclosure.

BRUCE ZG. COPPING.

References Cited the I file of this-patent UNITED STATES "PATENTS Number Name. Date 1,583,238. .Scudder May-.!l,.l926 2,072,166 Goodman Mar. 2, 1937 "2,193,923 Hillenzetal. Mar. 19, 19% 2,196,687 Steinfeld v .Apr. 9,1940 2,275,866 Runaldue. Mar. 10, 1942 2,440,052 Lingen etal. ..,.,Apr 20, 1948 2,481,612 Nicholson; Sept. 13, 1949 2,495,861 Newton Jan. .31, 195.0 2,537,121 Copping Jan. 9,1951 2,513,507 MacCracken Dec. "25, 1-951- 

